Inorganic fibrous products, in particular products made of glass fibers, are mainly made of continuous fibers (continuous glass fibers) or discontinuous fibers (short glass fibers). Among them, discontinuous fibers are generally used for a thermal insulation product. In this case, in order to form fiberized discontinuous fibers in a certain shape, a resin as a binder is applied to the discontinuous fibers to make the discontinuous fibers into a mat product, a plate product or a roll product, followed by partly or entirely coating or bonding e.g., a facing on such a product according to applications. These products are utilized as thermal insulation products for houses or general construction. An example of the other applications of the discontinuous fibers is an acoustical insulation product. Since finely fiberized discontinuous fibers effectively absorb a noise in the fibrous space made thereof, the finely fiberized discontinuous fibers can have an excellent advantage in noise suppression by being used in a sound insulation wall for, e.g., various buildings or roads.
In order to use discontinuous fibers to produce such a thermal insulation product or an acoustical insulation product, it is important to uniformly distribute fiberized discontinuous fibers on a collection conveyor. Heretofore, short glass fibers (hereinafter, sometimes abbreviated as “fibers”) fiberized by a spinner of a fiberizing unit are dropped in a hollow bucket disposed just under the spinner, to be formed into a bundle (hereinafter, referred to as “veil”) of short glass fibers, and the fibers are discharged from a circular opening of the hollow bucket into a collection zone (hereinafter, referred to as “hood”) to be uniformly distributed and collected on the collection conveyor. As a method for uniformly distributing the veil discharged from the hollow bucket on the collection conveyor, the following method has been known.
(1) Patent Document 1 discloses a method of alternately blowing compressed air to the veil from both sides of the veil so as to disperse and uniformly distribute the veil on a collection conveyor (hereinafter, referred to as an air dispersion system).
(2) Patent Document 2 and Patent Document 3 disclose a method of mechanically swinging the veil in a direction at right angles to the flow direction of a collection conveyor to disperse and uniformly distribute the veil on the collection conveyor (hereinafter, referred to as “a mechanical system”).
The above air dispersion system uses compressed air to uniformly distribute short glass fibers in a width direction of a collection conveyor. That is, as shown in FIG. 6, fibers fiberized by a spinner 1 of a fiberizing unit, after the veil 5 discharged from the hollow bucket 2 is sprayed with a binder by a binder applicator 12, flow down in a hood 11 while they are swung in a width direction of a collection conveyor and dispersed by blowing compressed air from both sides from an air blowing unit 18, so as to be uniformly collected on the collection conveyor 8 as a mat of fibers 7. Further, the compressed air blown is sucked through the collection conveyor 8 and is discharged and treated as an exhaust gas 9.
In the above method, fibers are likely to be stirred up in the hood since a large amount of compressed air is employed to disperse the fibers. The stirring up of fibers is a phenomenon showing the presence of agglomerated fibers floating in the space in the hood without being collected on the conveyor, when the fibers are collected on the conveyor. Since the above binder applied on the fibers is viscous and adhesive, fibers are likely to be agglomerated to form clusters of fibers in the space in the hood, or deposited on the fiberizing unit or equipments in the hood to form clusters of fibers, under a condition where fibers are greatly stirred up. As the clusters of fibers are getting larger in size, these clusters are likely to be dropped on the collected mat of fibers, whereby the quality of a product tends to be deteriorated, such being problematic.
Heretofore, in order to prevent clusters of fibers from being formed, it is required to periodically clean the inside of the hood, and in order to restrain fibers from being stirred up, it is required to make the fiber collecting apparatus larger. However, when the fiber collecting apparatus is made larger, the amount of exhaust gas increases, and huge energy is needed to clean up the exhaust gas. Although an attempt is made to increase the suction amount of the collection conveyor in order to restrain the stirring-up of fibers, huge energy is also needed since electric energy for a fan to be used for suction increases.
On the other hand, in the mechanical system, a hollow bucket is disposed under a fiberizing unit, and the bucket is swung in a direction (width direction) at right angles to the conveying direction of the collection conveyor, whereby short glass fibers dropped in the bucket are dispersed and collected on the collection conveyor. However, such a method had a problem that the frequency of mechanical failure increases since load to a mechanical moving part is increased as the bucket is swung for dispersing the short glass fibers. Further, there is a case where dispersibility is poor since the short glass fibers were dispersed merely by swinging the bucket.
Patent Document 1: JP-B-59-7652
Patent Document 2: JP-A-59-199855
Patent Document 3: WO2004/041736